Ring oscillators include logic gates or analog amplifiers connected in a loop, that is, in a ring configuration. The output of one element is connected to an input of the next. An odd number of these components invert their input signal. Ring oscillators have many uses in electronics, and they can be used as entropy sources to generate true random numbers used in information security. Synchronizable ring oscillators provide some advantages for information security applications. For example, synchronizable ring oscillators ensure stable startup conditions by running the ring oscillators in a short period when synchronizing the ring oscillators to a fixed clock frequency. In this way, the ring oscillators generate a known amount of heat, which guarantees predictable startup conditions necessary for proper operation of the ring oscillators in information security. After the ring oscillators are synchronized, the side channel leakage and interference injection sensitivity can be significantly reduced by shorter free running oscillation times in the normal (asynchronous) operation mode. Shorter free running oscillation times also improve the response time and throughput of information security applications.
One existing solution to synchronize a ring oscillator is to use operational amplifiers in the ring oscillator, and drive the non-inverting inputs of the operational amplifiers with narrow pulses derived from a clock signal. Another existing solution connects the ground lines of the input transistors of the ring gates to a wire, which is fed by pulses of the synchronization signal. However, neither of these existing solutions can be laid out by standard digital design tools in integrated circuits, sometimes referred to as chips.
Therefore it would be desirable to have a system and method that take into account at least some of the issues discussed above, as well as other possible issues.